1. Field of the Invention
The present invention relates to an communication apparatus, such as IP (Internet Protocol) communication apparatus, that performs communication over an IP network, such as the Internet and the like; an communication system; and a method for setting an IP address of the communication apparatus. The present invention particularly relates to an communication apparatus having a router function, such as a DHCP (Dynamic Host Configuration Protocol) server function and the like; an communication system including the communication apparatus; and a method for setting an IP address of the communication apparatus.
2. Description of Related Art
Conventionally, when communication apparatuses, such as an IP telephone apparatus and the like, are used to perform communication on an IP network, unique IP addresses need to be assigned in order to identify the apparatuses. For example, when communication apparatuses, which are provided on a predetermined LAN (Local Area Network), are connected to the Internet and the like via a relay device, such as a router and the like, a user (or a network administrator) of the communication apparatuses can manually set IP addresses on each of the apparatuses so as to avoid an IP address conflict among the apparatuses within the LAN. Instead of manual setting by a user, a method is known for automatically setting IP addresses via DHCP. In the method, communication apparatuses connected to a network can use IP addresses reserved on a predetermined DHCP server. The DHCP server dynamically assigns the IP addresses in response to a request from each apparatus such as when the apparatus starts. In addition, the DHCP server can retrieve the IP addresses assigned to the apparatuses that have completed communication, and reassign the IP addresses to other apparatuses.
In the above-described IP address assignment to the communication apparatuses, however, an IP address may conflict with an IP address of another apparatus, when, for example, a user erroneously assigns to a predetermined communication apparatus, an IP address already assigned to another apparatus as a fixed IP address, or when an communication apparatus starts, the apparatus being assigned with an IP address identical to an IP address assigned to another apparatus already connected to the network. Such IP address conflict may hamper proper transmission and reception of a packet, and thus causing a communication failure.
A conventional technology exists for detecting such IP address conflict. For instance, in a network system where a host that checks and detects an IP address conflict and a plurality of hosts to be checked are connected to a same LAN, the host that checks and detects the IP address conflict transmits to the hosts to be checked via the LAN, an ARP request packet that contains an IP address to be checked on a subnet same as the host that checks and detects the IP address conflict. The IP address conflict is detected based on whether or not an ARP reply packet is transmitted from the hosts to be checked to the host that checks and detects the IP address conflict via the LAN (refer to Related Art 1).
[Related Art 1] Japanese Patent Laid-open Publication 2001-244945
However, the conventional technology disclosed in above-described Related Art 1 requires a user to eliminate the IP address conflict when detected, such as by manually changing IP address setting of each apparatus. Further, even though the IP address conflict is eliminated, there may be a case where the same IP address is reassigned by the DHCP server, when the above-described DHCP server is used to assign the IP addresses to the apparatuses and the changed IP address is included in a range of the IP addresses reserved on the DHCP server, thereby repeating the same conflict.
Moreover, for an communication apparatus having a router function, such as, for example, a DHCP server function, IP addresses need to be assigned, so that an address space of IP addresses on a LAN, to which a plurality of network devices, such as a PC (personal computer) and the like, are connectable, does not conflict with an address space of WAN (Wide Area Network) IP addresses, which are obtained through the DHCP server and the like.